This research is designed to increase our understanding of gene control, particularly concerning genes expressed and necessary in low levels in all cells--known as "housekeeping" genes. The study of these genes is particularly relevant now as it appears some cancer genes may be members of this class. The project will focus on the mouse dihydrofolate reductase gene (dhfr) and will use methods of gene transfer to put mini-gene constructs of dhfr into animal cells to analyze their expression. Mutants of the mini-genes will be made by linker insertion and deletion in order to determine what functions various regions of the gene have. Three aspects of the dhfr gene locus will be studied: (1) the region of DNA involved in correct termination and processing and the region of DNA involved in transcription initiation will be analyzed. The region of transcription initiation is the same region that appears to serve as a promoter for a divergently transcribed gene; (2) the growth regulation of dhfr is posttranscriptional. The region of the DNA responsible for the regulation will be located and studied in an effort to understand the mechanism of growth regulation; (3) the nature of the divergently transcribed gene will be elucidated. A cDNA will be obtained and sequenced, the gene will be mapped, antibodies will be raised against the product of coding regions of the gene made as fusion proteins in E. coli, and expressing mini-genes will be made of the gene. (I)